Flexible conduit for high-pressure fluid



Patented June 8, 1954 FLEXIBLE CONDUIT FOR HIGH-PRESSURE FLUID John A.Zublin, Los Angeles, Calif.

Application May 14, 1952, Serial No. 287,663

2 Claims.

The present invention relates to an assembly for providing a flexibleconduit for the conveying of high pressure fluids and through the mediumof which assembly a positive drive may be effected.

More specifically, the invention contemplates the provision of aflexible drill string section adapted to be interposed between anormally substantially rigid rotary drill string and a drill bit.

It is still a further and more specific object and purpose of theinvention to provide a tubular, rotary drill string section through themedium of which a rotary bit may be positively driven while permittingflexing of the drill string section in all directions.

It is a more specific purpose and object of the invention to provide arotary, flexible drill string section made up of a multiplicity of unitswith universal couplings therebetween so arranged as to permit each unitto partake of limited angular movement in all directions with respect tothe next adjacent unit while positively transmitting rotary motionthrough all of said units.

It is a still further purpose and object of the invention to provide amultiple unit, relatively flexible, rotary drill string section for theconveyance of high pressure drilling fluid with minimum frictionalresistance to relative angular movement of the units making up therotary drill string section.

Further and more specific objects of the invention will become apparentas the description proceeds which will be given in conjunction with theaccompanying drawings, wherein Figure 1 is a view in side elevationillustrating the invention,

Figure 2 is a detailed cross-sectional view taken through the center ofFigure 1 at right angles thereto,

Figure 3 is a detailed cross-sectional view on the line 33 of Figure 2,

Figure 4 is a detailed cross-sectional view on the line 4-5 of Figure 2,and

Figure 5 is an enlarged cross-sectional view illustrating the structuraldetails of a permissible variant of one of the universal couplingsembraced in the flexible drill string section of the present invention.

Referring to Figure 1, the flexible drill string section is illustratedas made up of units It, I I and !2. It will be understood that theintermediate unit 5 I may be multiplied to any desired extent to providea flexible, rotary drill string section of predetermined desired length.All intermediate units will be identical and conform to the constructionof section ll.

The adjacent ends of juxtaposed units have intermeshing teeth. Forexample, the sub section It has the teeth 13 which are adapted to fitbetween and interengage teeth M at the upper end of the unit ll Thelower end of the unit I l is provided with similar teeth l5 that engagebetween complementary teeth IG at the upper end of the unit l2. It willbe observed that the teeth l5 at the lower end of the unit H arecircumferentially displaced with respect to the teeth M at the upper endof the unit I l as indicated at a, Figure 1. This is to insure that thevarious points of interconnection will not lie in the same verticalplanes. The sub unit it is provided with a threaded pin Il adapted to bereceived in the lower end of the lowermost section of a substantiallyrigid, rotary drill string. The lower unit l2 thatwill be seen byreference to Figure 2 is provided with an interiorly threaded recess 18for threadedly receiving the shank of a rotary bit. When the shank ofthe rotary bit has been threaded into the recess [8 of the lower unit i2and the threaded pin H has been mounted at the lower end of a normallyrigid, rotary drill string, the entire unit may be rotated from thesurface of the well to positively drive the bit carried at the lower endof the assembly.

Referring to Figure 2, it will be observed that the unit I! embraces anupper member i9 and a lower member 20 threadedly interengaged at 2! andsecured by the weld 22. The upper member i9 is provided with a centralchannel extending from end to end thereof and of variable diameter forpurposes to be hereinafter described. The lower member 20 is alsoprovided with a tubular channel of special construction. The curvedsurface 23 and the curved surface 24 of the member 29 together providean outer socket Within which the outer ball 25 is received. The ball 25has a tubular extension 25 that extends well below the lower end of themember 29 to provide means for attachment to the next adjacent unit suchas 12. The arrangement is such that the unit i2 may partake of movementin any direction with respect to unit II and the ball 25 with its socket23, 24 providing a universal coupling. Ball 25 and tubular extension 26thereof provide a central channel for the passage of drilling fluid.Interiorly of the hollow ball 25 there is provided a frusto-conicalsurface 21 which constitutes an annular seat for the inner ball 28. Theinner ball 23 and the outer ball 25 have a common center 29. Thespherical surface of the inner ball 28 contacts the frusto-conical seat2? only over a very limited surface. The inner ball 28 is provided witha tubular extension 3 8 wholly within the channel extending through theupper member I9 of the unit it. The tubular extension 39 of the ball 23is provided with the outwardly projecting annular flange 3i and there iscompressed between this flange 3! and the shoulder 32 in the channel ofmember l9 a resilient ring 33 which constantly resiliently urges theball 28 downwardlywith its spherical surface forced into contact withthe frustoconical seat 2'! on the interior of the outer ball 25.

The high pressure fluid which moves through the upwardly projectingtubular extension 39 of the inner ball 28 and thence through the tubularextension 26 of the outer ball 25 is effectively prevented from leakageby two important expedients; first, the spherical surface of the ball 28is constantly resiliently urged against the frusto-conical seat 21 and,secondly, low pressure areas in the direction of flow or" the highpressure fluid are created at those points in the assembly at whichleakage might most likely be expected to occur. It will be observed thatthe channel through the interior of the upper member IQ of unit H is ofreduced cross section in the direction of flow of fluid as indicated at34, whereas the extreme upper end of the tubular extension 30 of theinner ball 28 is flared outwardly as indicated at 35 so that as fluidmoves downwardly through member I?) and into the tubular extension 33 ofthe inner ball 28 a Venturi action is created at the upper end of the.tubular extension 38 of ball 28 and a low pressure area or zone resultswhich inhibits leakage downwardly around the upper end of the tubularextension 30 and the resilient ring 33. The same action occurs at thepoint where fluid moves into the upper end of the tubular extension 38from the inner channel of the threaded stem 1'! indicated at 36 inFigure 2.

It will also be observed that the inner channel 31 of the tubularextension 36 of the outer ball 25 is of substantially greater diameterthan the inner channel of the tubular extension 30 of the inner ball 28.It follows that as fluid moves under pressure downwardly from theinterior of the inner ball 28 into the inner channel 3? of the tubularextension 26 of the outer ball 25 a further Venturi action is createdforming a low pressure area or zone just below the point of contactbetween the inner ball 28 and the frustoconical seat 27, which line ofcontact is indicated at X in Figure 5. The low pressure zone thuscreated at the upper end of the tubular extension 30 and immediatelybelow the inner ball 28 tends to prevent any leakage of the highpressure fluid from the inner channel through which it flows andtherefore prevents contact of high pressure fluid with the outer ball 25and the socket surfaces 23 and 24. With this construction no greatpressure need be maintained between the surface of the ball 25 and thesocket surfaces 23 and 24 whereby little frictional resistance toangular movement of ball 25 with respect to surfaces 23 and 24 isencountered.

Inasmuch as the contact area between the inner ball 28 and thefrusto-conioal seat 27 is practically linear and of limited extent,little resistance to relative movement of the inner ball 28 over thefrusto-conical seat is encountered, even though a liquid-tight cell ismaintained at this point of the structure.

In all angular positions of the units making up the flexible drillstring section of the present invention the inter-engaging teeth such asl3 and id and I5 and i6 impart a positive driving action from end to endof the flexible drill string section.

To insure a firm interlock between units the lower end of the tubularextension 26 of the outer ball 25 is exteriorly threaded as indicated at31 to be threadedly received in the socket of the juxtaposed member ofthe next unit such as the member 22 of unit H. A transverse hole may bedrilled through the structure as indicated more specifically at 38 ofFigure 4 and a locking pin 39 welded in place therein so as to firmlyinterlock the units of the flexible drill string section.

The expression inner ball as used herein is intended to embracepermissible variants such as shown in Figure 5 where the contact surfaceof the inner ball is spherical and concentric with the outer ball.

From the foregoing it will be observed that I have provided an assemblyfor a flexible drill string section that permits the conveyance of thehigh pressure drilling fluid without leakage and without requiring theexertion of excessive pressure over large contacting surfaces such as toinhibit easy angular movement of juxtaposed units of the flexible drillstring section.

Having thus described my invention, what I claim is:

1. A pressure fluid conducting assembly comprising first and secondgenerally tubular units interconnected in end to end relationship by auniversal joint structure, said universal joint structure comprising anouter socket in the first of said units, an outer ball on the end of thesec 0nd of said units and positioned in said socket, an annular seatwithin said outer ball, an inner ball 3 within said outer ball andseating on said annular seat, a tubular extension on said inner balltelescoping into said first tubular unit, there being a fluid passagewayextending longitudinally through said tubular units, through said outerand inner balls and through said tubular extensicn, an annular flange onthe exterior of said tubular extension, an annular shoulder on theinterior of said first tubular unit, and a cylindrical resilient packingmember sealingly engaging the exterior surface of said tubular extensionand the interior surface of said first tubular-unit to prevent fluidleakage between said tubular extension and said first tubular unit, saidpacking member being longitudinally compressed between said shoulder andsaid flange to urge said inner ball into seating engagement with saidannular seat and said packing member.

2. A fluid conducting assembly as defined by claim 1 in which said firstand second tubular units have loosely interengaging teeth at theiradjacent ends to permittransmission of torque from one to the other ofthe units.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 149,842 Deeds Apr. 21, 1874 1,018,143 Vissering Feb. 20, 19121,611,467 Lonsdale Dec. 21, 1926 1,772,547 Keese et al. Aug. 12, 19301,827,432 Hundemer Oct. 13, 1,931

